The long-term goal of this study is to chromosomally localize genes that raise risk for epilepsy. The overall experimental design consists of linkage anaylsis of susceptibility to epilepsy. This invloves searching for associations within families between histories of epilepsy and genetic markers detected in DNA samples. The statistical approach involves maximum likelihood estimation of the recombination fraction and odds of genetic linkage of a putative susceptibility gene for epilepsy to each genetic marker. The research material to be obtained includes (1) interviews, (2) blood samples, (3) neurological examinations (subjects who have had seizures only), (4) EEGs (subjects known or suspected to have epilepsy only), and (5) medical records (subjects known or suspected to have had seizures only). Blood samples for genotype determination will be collected from individuals with epilepsy and from some or all of their parents, siblings, offspring, and spouses (depending on the constellation of affected indivduals in the family). Genotypes will be determined at each of a series of 400 microsatellite markers spaced at an average of 10 centimorgan intervals throughout the genome.